a) Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device wherein liquid crystal molecules are vertically aligned (homeotropic alignment) between opposing substrates when no electric field is applied and one pixel is divided into a plurality of domains.
b) Description of the Related Art
FIGS. 25A to 25C are schematic cross sectional views of a conventional liquid crystal display device of a homeotropic alignment type, respectively illustrating a black display state, a halftone display state, and a white display state. Liquid crystal material containing liquid crystal molecules having a negative dielectric anisotropy is filled in between a pair of substrates 100 and 101. Polarizer plates are disposed outside of the substrates 100 and 101, with their polarizing axes crossing at a right angle.
As shown in FIG. 25A, when a voltage is not applied, the liquid crystal molecules 102 are aligned vertically relative to the substrates 100 and 101 and produce black color. As a voltage is applied across the substrates to align the liquid crystal molecules 102 in parallel to the substrates as shown in FIG. 25C, the polarization direction of light passing through the liquid crystal layer rotates and white color is produced.
As shown in FIG. 25B, as a voltage is applied which is lower than that when the white image is produced, the liquid crystal molecules 102 are aligned obliquely relative to the substrate. A halftone image is obtained by light L1 propagating along a direction perpendicular to the substrates. Light propagating from the lower right to upper left as viewed in FIG. 25B rarely receives the birefringence effect of the liquid crystal layer. Therefore, when the display screen is viewed from the upper left, it becomes black. Contrary, light propagating from the lower left to upper right as viewed in FIG. 25B considerably receives the birefringence effect of the liquid crystal layer. Therefore, when the display screen is viewed from the upper right, it becomes white. As above, a homeotropic type liquid crystal display device is generally has poor visual angle characteristics in the halftone display state.
The visual angle characteristics of a conventional homeotropic type liquid crystal are poor in the halftone display state, as described above.